Measurement Of High Resistance by Megohm Bridge method

  Procedure:

  1. Apply Supply voltage 500V or 1000V.

  2. Set the unknown resistance values Rab, Rag, Rbg from 'Set Resistor Value' tab by clicking on 'Set' button.

  3. Then switch on the supply to get millivoltmeter deflection.

  4. Change the bridge resistances (P, Q, and S) until the null deflection is occurred.

  5. Observe the millivoltmeter pointer to achieve "Null"

  6. If "Null" is achieved, switch to 'Measure Resistor value' tab and   click on 'Simulate'. Observe calculated values of unknown   Resistor (Rab).

    7. N.B.:-
    Range of P = 1 `Ω` to `10^8 Ω` (in steps of 5`Ω`).
    Range of Q = 1 `Ω` to `10^8 Ω` (in steps of 5`Ω`).
    Range of S = `10^3 Ω` to `10^8 Ω` (in steps of 5`Ω`).

Tutorials Point

Voltage:

V

`Ω`

`Ω`

`Ω`

`mV`

  • `Ω`

    `Ω`

    `Ω`

    Set the actual value of unknown resistor to be measured
    Enter the unknown resistance values Rab, Rag, Rbg
    and then click on the "Set" button.
    Rab (in `Ω`):  `10^3Ω`   `10^5MΩ`
    Rag (in `Ω`):  `10^3Ω`   `10^5MΩ`
    Rbg (in `Ω`):  `10^3Ω`   `10^5MΩ`
  • The current voltmeter reading is:   mv.

    Now click on "Simulate" to get:
    Unknown Resistance value Rab(in `Ω`):
CONTROLS
   P : 1Ω     1000M`Ω`
   Q : 1Ω     1000M`Ω`
   S : 1000Ω     1000M`Ω`